I learned all this from my drama and screenwriting teacher, who knows a thing or two about plays, seeing as how he works in the theatre. :)
How to Format Plays
So I won't beat around the bush here; knowing how to format your play makes a difference. It will look a lot clearer and will be easier to read. So open up Microsoft Word or Notepad (whichever you have, though Word will work better) and let's get started. Recommended fonts are Times New Roman or Courier New, font size 12.
If you're writing a stage play, then you'll need to know stage instructions, and that's the trickiest part. Think in opposites. Stage right (stage R) is going to be on the left looking from the audience, stage left (stage L) is going to be on the right. Then there's center stage (C), which is… well, in the center. Upper stage (U) is going to be farther away from the audience, and down stage (D) is going to be closer. Then at the back you'll have UR (upper right), URC (upper right center), UC (up center), ULC (upper left center), and UL (upper left). Then it will follow downstage respectively, so the stage will look like this:
UR URC UC ULC UL
R RC C LC L
DR DRC DC DLC DL
Hopefully that makes sense.
For sake of example, I'll use my play, "Stockholm Syndrome."
At the top of the page, you'll have a description of your setting.
Scene/Setting (whichever): An office. The walls are light blue and the floor is dark blue. There's a mahogany desk to stage R and there's also a chair. On the desk are a phone and a box of papers. There's a window with a dark blue curtain by the desk, and next to the window is a painting.
When you start the scene, you'll tab six times to get it in the middle of the page. Word will want to go back to left aligned, so when it does that, just hit tab six times again on the new line and that'll fix it so it's properly formatted. FictionPress won't show the tabbing, so when you upload it, just put the actions and descriptions in the middle. Also, after the setting, everything but the dialogue and character names are going to be in parentheses. Also, unless in dialogue, character names are going to be capitalized and center spaced- no colons necessary.
(CHARLIE is sitting at the desk, talking on the phone. CHARLIE is in his early twenties and has a wide-eyed innocence about him. As he's talking, he's playing with a yo-yo)
That's easy enough. :) Now for dialogue and description in dialogue.
Yeah Mom… uh-huuuhhhmmm… I know… I know… Moootherrr!
(He rolls his eyes and sighs. He drops the yo-yo and scrambles up from his chair to get it, almost knocking everything else in the process)
Yeah… no… no, everything… everything's fine, Mom! I just tripped over my chair, is all. Yeah…. No, I'm fine…. No, Mom, an ambulance is not neces… no Mom, I'm not bleeding… I'm not dying! Oh I wish I was… no, I didn't say anything…
(There's a knock at the door)
I gotta go… Goodbye. I love you. Good…bye.
(Hangs up, collapses in chair, letting the yo-yo unwind to the floor. Takes a deep breath)
OK, sorry for the long ol' chunk of scene. When you're first inserting dialogue, it's going to be directly under the character's name, not two lines under. If you're putting in an action for the character, then put it between the name and dialogue tabbed and in parentheses.
If you're putting description and or actions between dialogue, just tab it, put it in parentheses, then go back to left aligned for the dialogue. Unless a new character is talking, then you don't need to put in the name again.
Speaking of new characters… when you're introducing a new character, then… I'm sure you can guess. All together, class!
"Tab it, parenthesize it, add in actions and descriptions."
(JULIA enters from R, holding a cactus… blablabla, you get the picture)
You don't need to do anything special after adding the new character; just do what's already been said about dialogue and description.
The last thing you need to do when you've finished a scene or your play, center space it and type "BLACKOUT." That doesn't need to be in caps, but that's the habit I fell into.
And most importantly: KNOW YOUR GRAMMAR. Make sure you haven't confused any homophones, check for typos, make sure you have some sort of punctuation mark at the end of each sentence (unless it's the last sentence in the parentheses). If grammar isn't your strong point, then find someone who will check it for you. Don't rely on Word's grammar check; it's not that trustworthy.
So hopefully this helped. If you have any questions, just leave it in a review.
Now have some cookies and other assorted baked goods. :)